Method for controlling a power driver

Abstract

A driving tool having a driver, a power source, a sensor and a controller. The power source selectively provides an input to the driver to cause the driver to translate along an axis. The sensor senses a condition in the power source that is indicative of a level of kinetic energy of an element in the power source and generates a sensor signal in response thereto. The controller is coupled to the power source and the sensor and is responsive to the sensor signal for deactivating the power source to inhibit the power source from providing the input to the driver when the level of kinetic energy of the element in the power source is below a predetermined threshold. A method for operating a driving tool is also provided.

1. A method comprising:
 providing a driving tool having a driver and a motor assembly, the driver being movable along an axis, the motor assembly including an output member and a pinch member, wherein the motor assembly includes a motor; 
 operating the motor assembly to move the output member; 
 determining a kinetic energy level of the moving output member based on a rotational speed of an element in the motor assembly, the kinetic energy level of the moving output member being determined as a function of the back electromotive force produced by the motor; and 
 moving the pinch member to drive the driver into contact with the output member to transmit power from the output member to the driver if the kinetic energy level exceeds a predetermined threshold; 
 wherein determining a kinetic energy level of the moving output member includes: 
 determining a temperature of at least a portion of the driving tool; and 
 determining an approximated speed of the motor based at least partially on the back electromotive force and the temperature. 
 
     
     
       2. The method of  claim 1 , wherein the pinch member is a roller. 
     
     
       3. The method of  claim 1 , wherein the approximated speed of the motor is determined from the equation
     S=S   BEF   −ΔS   T    
 
       wherein S is the approximated speed of the motor, S BEF  is a rotational speed of the motor based solely on the back electromotive force, and ΔS T  is a speed differential that is based on a slope of a line that is representative of an actual rotational speed of the motor when the back electromotive force of the motor is held constant and the temperature is varied. 
     
     
       4. The method of  claim 1 , wherein the approximated speed of the motor is also at least partially based on a voltage of a battery that supplies electrical energy for the motor. 
     
     
       5. The method of  claim 4 , wherein the approximated speed of the motor is determined from the equation
     S=|S   BATV   +ΔS   T   −ΔS   BEF | 
 
       wherein S is the approximated speed of the motor, S BATV  is a rotational speed of the motor based on a voltage of the battery, ΔS BEF  is a term that is based upon the back- emf produced by the motor, and ΔS T  is a speed differential that is based on a slope of a line that is representative of an actual rotational speed of the motor when the temperature is varied. 
     
     
       6. The method of  claim 1 , further comprising generating at least one of a visual signal and an audio signal when the kinetic energy level does not exceed the predetermined threshold. 
     
     
       7. A method comprising:
 providing a driving tool having a driver and a motor assembly having a motor, a flywheel, which is driven by the motor, and a pinch member; 
 operating the motor to thereby turn the flywheel; 
 sensing a back electromotive force of the motor; 
 determining a temperature of at least a portion of the driving tool; 
 determining the speed of the motor based at least partially on the back electromotive force and the temperature; and 
 if a rotational speed of the flywheel exceeds a predetermined threshold, moving the pinch member to drive one of the flywheel and the driver into contact with the other one of the flywheel and the driver to transmit energy from the flywheel to the driver and translate the driver along an axis. 
 
     
     
       8. The method of  claim 7 , wherein the speed of the motor is determined from the equation
     S=S   BEF   −ΔS   T    
 
       wherein S is the speed of the motor, S BEF  is a rotational speed of the motor based solely on the back electromotive force, and ΔS T  is a speed differential that is based on a slope of a line that is representative of an actual rotational speed of the motor when the back electromotive force of the motor is held constant and the temperature is varied. 
     
     
       9. The method of  claim 7 , wherein the speed of the motor is also at least partially based on a voltage of a battery that supplies electrical energy for the motor. 
     
     
       10. The method of  claim 9 , wherein the speed of the motor is determined from the equation
     S=|S   BATV   +ΔS   T   −ΔS   BEF | 
 
       wherein S is the speed of the motor, S BATV  is a rotational speed of the motor based on a voltage of the battery, ΔS BEF  is a term that is based upon the back-emf produced by the motor, and ΔS T  is a speed differential that is based on a slope of a line that is representative of an actual rotational speed of the motor when the temperature is varied. 
     
     
       11. The method of  claim 7 , further comprising generating at least one of an audio signal and a visual signal if after operating the motor the speed of the flywheel is not above the predetermined threshold speed. 
     
     
       12. A driving tool comprising:
 a driver that is movable along an axis; 
 a power source having a motor, a flywheel that is driven by the motor, and a pinch roller that is movable between a first position, in which the pinch roller is not urging the driver into engagement with the flywheel, and a second position in which the pinch roller urges the driver into direct driving contact with the flywheel; 
 a sensor for sensing a condition in the power source and generating a sensor signal in response thereto, the condition being indicative of a level of kinetic energy of an element in the power source; and 
 a controller coupled to the power source and the sensor, the controller being responsive to the sensor signal for deactivating the power source to inhibit movement of the pinch roller into the second position when the level of kinetic energy of the element in the power source is below a predetermined threshold; 
 wherein the characteristic of the power source is a rotational speed of the element and wherein the sensor is selected from a group of sensors consisting of sensors that sense a back electromotive force generated by the motor and eddy current sensors. 
 
     
     
       13. The driving tool of  claim 12 , wherein the sensor is an eddy current sensor. 
     
     
       14. The driving tool of  claim 12 , wherein the controller generates at least one of a visual signal and an audio signal when the level of kinetic energy of the element in the power source is below the predetermined threshold. 
     
     
       15. The driving tool of  claim 12 , further comprising a magazine and a fastener sensor, the magazine being operable for holding one or more of fasteners, the fastener sensor being operable for sensing a condition wherein a quantity of the fasteners that are stored in the magazine is less than a predetermined quantity, the fastener sensor responsively generating a fastener sensor signal when the condition is sensed. 
     
     
       16. The driving tool of  claim 3 , wherein the controller receives the fastener sensor signal and responsively generates at least one of a visual signal and an audio signal. 
     
     
       17. The driving tool of  claim 3 , wherein the controller receives the fastener sensor signal and responsively deactivates the power source to thereby inhibit the power source from providing the input to the driver.